Table of Contents
Xserver - X Window System display server
X [option ...]
X is the generic name for the X Window System
display server. It is frequently a link or a copy of the appropriate server
binary for driving the most frequently used server on a given machine.
The X server is usually started from the X Display Manager program
or a similar display manager program. This utility is run from the
system boot files and takes care of keeping the server running, prompting
for usernames and passwords, and starting up the user sessions.
that run more than one window system may need to use the xinit(1)
instead of a display manager. However, xinit is to be considered a tool
for building startup scripts and is not intended for use by end users.
Site administrators are strongly urged to use a display manager, or build
other interfaces for novice users.
The X server may also be started directly
by the user, though this method is usually reserved for testing and is
not recommended for normal operation. On some platforms, the user must
have special permission to start the X server, often because access to
certain devices (e.g. /dev/mouse) is restricted.
When the X server starts
up, it typically takes over the display. If you are running on a workstation
whose console is the display, you may not be able to log into the console
while the server is running.
Many X servers have device-specific command
line options. See the manual pages for the individual servers for more
details; a list of server-specific manual pages is provided in the SEE ALSO
All of the X servers accept the command line options described
below. Some X servers may have alternative ways of providing the parameters
described here, but the values provided via the command line options should
override values specified via other mechanisms.
Some X servers accept the following options:
- The X server
runs as the given displaynumber, which by default is 0. If multiple X servers
are to run simultaneously on a host, each must have a unique display number.
See the DISPLAY NAMES section of the X(7)
manual page to learn how to
specify which display number clients should try to use.
- -a number
- sets pointer
acceleration (i.e. the ratio of how much is reported to how much the user
actually moved the pointer).
- disables host-based access control mechanisms.
Enables access by any host, and permits any host to modify the access
control list. Use with extreme caution. This option exists primarily for
running test suites remotely.
- -audit level
- sets the audit trail level. The
default level is 1, meaning only connection rejections are reported. Level
2 additionally reports all successful connections and disconnects. Level
4 enables messages from the SECURITY extension, if present, including generation
and revocation of authorizations and violations of the security policy.
Level 0 turns off the audit trail. Audit lines are sent as standard error
- -auth authorization-file
- specifies a file which contains a collection
of authorization records used to authenticate access. See also the xdm(1)
- disables backing store support on all
- sets the default root window to solid black instead of the standard
root weave pattern.
- turns off key-click.
- c volume
- sets key-click volume (allowable
- -cc class
- sets the visual class for the root window of color
screens. The class numbers are as specified in the X protocol. Not obeyed
by all servers.
- causes the server to generate a core dump on fatal
- -deferglyphs whichfonts
- specifies the types of fonts for which the
server should attempt to use deferred glyph loading. whichfonts can be
all (all fonts), none (no fonts), or 16 (16 bit fonts only).
- -dpi resolution
- sets the resolution for all screens, in dots per inch. To be used when the
server cannot determine the screen size(s) from the hardware.
DPMS (display power management services), where supported. The default
state is platform and configuration specific.
- disables DPMS (display
power management services). The default state is platform and configuration
- disables named extension. If an unknown
extension name is specified, a list of accepted extension names is printed.
- enables named extension. If an unknown extension
name is specified, a list of accepted extension names is printed.
- -f volume
- sets feep (bell) volume (allowable range: 0-100).
- -fc cursorFont
- sets default
- -fn font
- sets the default font.
- -fp fontPath
- sets the search path
for fonts. This path is a comma separated list of directories which the
X server searches for font databases. See the FONTS section of this manual
page for more information and the default list.
- prints a usage message.
- causes all remaining command line arguments to be ignored.
- sets the maximum big request to size MB.
- -nolisten trans-type
a transport type. For example, TCP/IP connections can be disabled with
-nolisten tcp. This option may be issued multiple times to disable listening
to different transport types.
- prevents a server reset when the last
client connection is closed. This overrides a previous -terminate command
- -p minutes
- sets screen-saver pattern cycle time in minutes.
- permits the server to continue running if it fails to establish all of
its well-known sockets (connection points for clients), but establishes
at least one. This option is set by default.
- causes the server to exit
if it fails to establish all of its well-known sockets (connection points
- turns off auto-repeat.
- turns on auto-repeat.
the stipple with the classic stipple and cursor visible. The default is
to start with a black root window, and to suppress display of the cursor
until the first time an application calls XDefineCursor(). For the Xorg
server, this also sets the default for the DontZap option to FALSE. For
kdrive servers, this implies -zap.
- -s minutes
- sets screen-saver timeout time
- disables save under support on all screens.
- -t number
pointer acceleration threshold in pixels (i.e. after how many pixels pointer
acceleration should take effect).
- causes the server to terminate
at server reset, instead of continuing to run. This overrides a previous
-noreset command line option.
- -to seconds
- sets default connection timeout
- disables all testing extensions (e.g., XTEST, XTrap, XTestExtension1,
- ignored, for servers started the ancient way (from init).
- sets video-off screen-saver preference.
- sets video-on screen-saver preference.
- forces the default backing-store of all windows to be WhenMapped. This
is a backdoor way of getting backing-store to apply to all windows. Although
all mapped windows will have backing store, the backing store attribute
value reported by the server for a window will be the last value established
by a client. If it has never been set by a client, the server will report
the default value, NotUseful. This behavior is required by the X protocol,
which allows the server to exceed the client's backing store expectations
but does not provide a way to tell the client that it is doing so.
the default root window to solid white instead of the standard root weave
- -x extension
- loads the specified extension at init. This is a no-op
for most implementations.
- enables(+) or disables(-) the XINERAMA
extension. The default state is platform and configuration specific.
- -ld kilobytes
- sets the data space limit of the server to the specified number of kilobytes.
A value of zero makes the data size as large as possible. The default value
of -1 leaves the data space limit unchanged.
- -lf files
- sets the number-of-open-files
limit of the server to the specified number. A value of zero makes the limit
as large as possible. The default value of -1 leaves the limit unchanged.
- -ls kilobytes
- sets the stack space limit of the server to the specified
number of kilobytes. A value of zero makes the stack size as large as possible.
The default value of -1 leaves the stack space limit unchanged.
on the X Window System logo display in the screen-saver. There is currently
no way to change this from a client.
- turns off the X Window System
logo display in the screen-saver. There is currently no way to change this
from a client.
- default|mono|gray|color sets the color allocation policy
that will be used by the render extension.
- selects the default policy
defined for the display depth of the X server.
- don't use any color
- use a gray map of 13 color cells for the X render extension.
- use a color cube of at most 4*4*4 colors (that is 64 color cells).
X servers that support XDMCP have
the following options. See the X Display Manager Control Protocol specification
for more information.
- disables smart scheduling on platforms that support the smart
- -schedInterval interval
- sets the smart scheduler's scheduling interval
to interval milliseconds.
X servers that support the XKEYBOARD
(a.k.a. "XKB") extension accept the following options. All layout files specified
on the command line must be located in the XKB base directory or a subdirectory,
and specified as the relative path from the XKB base directory. The default
XKB base directory is /usr/lib/X11/xkb.
- -query hostname
- enables XDMCP and sends Query packets
to the specified hostname.
- enable XDMCP and broadcasts BroadcastQuery
packets to the network. The first responding display manager will be chosen
for the session.
- -multicast [address [hop count]]
- Enable XDMCP and multicast
BroadcastQuery packets to the network. The first responding display
manager is chosen for the session. If an address is specified, the multicast
is sent to that address. If no address is specified, the multicast is
sent to the default XDMCP IPv6 multicast group. If a hop count is specified,
it is used as the maximum hop count for the multicast. If no hop count
is specified, the multicast is set to a maximum of 1 hop, to prevent the
multicast from being routed beyond the local network.
- -indirect hostname
- enables XDMCP and send IndirectQuery packets to the specified hostname.
- -port port-number
- uses the specified port-number for XDMCP packets, instead
of the default. This option must be specified before any -query, -broadcast,
-multicast, or -indirect options.
- -from local-address
- specifies the local address
to connect from (useful if the connecting host has multiple network interfaces).
The local-address may be expressed in any form acceptable to the host platform's
- causes the server to terminate (rather
than reset) when the XDMCP session ends.
- -class display-class
- XDMCP has an
additional display qualifier used in resource lookup for display-specific
options. This option sets that value, by default it is "MIT-Unspecified"
(not a very useful value).
- -cookie xdm-auth-bits
- When testing XDM-AUTHENTICATION-1,
a private key is shared between the server and the manager. This option
sets the value of that private data (not that it is very private, being
on the command line!).
- -displayID display-id
- Yet another XDMCP specific value,
this one allows the display manager to identify each display so that it
can locate the shared key.
The X server supports client connections via
a platform-dependent subset of the following transport types: TCP/IP, Unix
Domain sockets, DECnet, and several varieties of SVR4 local connections.
See the DISPLAY NAMES section of the X(7)
manual page to learn how to
specify which transport type clients should try to use.
X server implements a platform-dependent subset of the following authorization
protocols: MIT-MAGIC-COOKIE-1, XDM-AUTHORIZATION-1, XDM-AUTHORIZATION-2, SUN-DES-1,
and MIT-KERBEROS-5. See the Xsecurity(7)
manual page for information on
the operation of these protocols.
- [+-]accessx [ timeout [ timeout_mask
[ feedback [ options_mask ] ] ] ]
- enables(+) or disables(-) AccessX key
- -xkbdir directory
- base directory for keyboard layout files. This
option is not available for setuid X servers (i.e., when the X server's real
and effective uids are different).
- -ardelay milliseconds
- sets the autorepeat
delay (length of time in milliseconds that a key must be depressed before
- -arinterval milliseconds
- sets the autorepeat interval
(length of time in milliseconds that should elapse between autorepeat-generated
- -xkbmap filename
- loads keyboard description in filename on server
Authorization data required by the above
protocols is passed to the server in a private file named with the -auth
command line option. Each time the server is about to accept the first
connection after a reset (or when the server is starting), it reads this
file. If this file contains any authorization records, the local host is
not automatically allowed access to the server, and only clients which
send one of the authorization records contained in the file in the connection
setup information will be allowed access. See the Xau manual page for a
description of the binary format of this file. See xauth(1)
of this file, and distribution of its contents to remote hosts.
The X server
also uses a host-based access control list for deciding whether or not to
accept connections from clients on a particular machine. If no other authorization
mechanism is being used, this list initially consists of the host on which
the server is running as well as any machines listed in the file /etc/Xn.hosts,
where n is the display number of the server. Each line of the file should
contain either an Internet hostname (e.g. expo.lcs.mit.edu) or a DECnet hostname
in double colon format (e.g. hydra::) or a complete name in the format family:name
as described in the xhost(1)
manual page. There should be no leading or
trailing spaces on any lines. For example:
Users can add or remove hosts from this list and enable or disable access
control using the xhost command from the same machine as the server.
the X FireWall Proxy (xfwp) is being used without a sitepolicy, host-based
authorization must be turned on for clients to be able to connect to the
X server via the xfwp. If xfwp is run without a configuration file and
thus no sitepolicy is defined, if xfwp is using an X server where xhost
+ has been run to turn off host-based authorization checks, when a client
tries to connect to this X server via xfwp, the X server will deny the
connection. See xfwp(1)
for more information about this proxy.
The X protocol
intrinsically does not have any notion of window operation permissions
or place any restrictions on what a client can do; if a program can connect
to a display, it has full run of the screen. X servers that support the
SECURITY extension fare better because clients can be designated untrusted
via the authorization they use to connect; see the xauth(1)
for details. Restrictions are imposed on untrusted clients that curtail
the mischief they can do. See the SECURITY extension specification for
a complete list of these restrictions.
Sites that have better authentication
and authorization systems might wish to make use of the hooks in the libraries
and the server to provide additional security models.
The X server
attaches special meaning to the following signals:
The X server can obtain fonts
from directories and/or from font servers. The list of directories and font
servers the X server uses when trying to open a font is controlled by the
- This signal causes
the server to close all existing connections, free all resources, and restore
all defaults. It is sent by the display manager whenever the main user's
main application (usually an xterm or window manager) exits to force the
server to clean up and prepare for the next user.
- This signal causes
the server to exit cleanly.
- This signal is used quite differently
from either of the above. When the server starts, it checks to see if it
has inherited SIGUSR1 as SIG_IGN instead of the usual SIG_DFL. In this
case, the server sends a SIGUSR1 to its parent process after it has set
up the various connection schemes. Xdm uses this feature to recognize when
connecting to the server is possible.
The default font path is /usr/lib/X11/fonts/misc/, /usr/lib/X11/fonts/TTF/,
/usr/lib/X11/fonts/OTF, /usr/lib/X11/fonts/Type1/, /usr/lib/X11/fonts/100dpi/,
A special kind of directory can be specified
using the catalogue: prefix. Directories specified this way can contain
symlinks pointing to the real font directories. See the FONTPATH.D section
The font path can be set with the -fp option or by xset(1)
the server has started.
You can specify a special kind of font
path in the form catalogue:<dir>. The directory specified after the catalogue:
prefix will be scanned for symlinks and each symlink destination will be
added as a local fontfile FPE.
The symlink can be suffixed by attributes
such as 'unscaled', which will be passed through to the underlying fontfile
FPE. The only exception is the newly introduced 'pri' attribute, which will
be used for ordering the font paths specified by the symlinks.
75dpi:unscaled:pri=20 -> /usr/share/X11/fonts/75dpi
ghostscript:pri=60 -> /usr/share/fonts/default/ghostscript
misc:unscaled:pri=10 -> /usr/share/X11/fonts/misc
type1:pri=40 -> /usr/share/X11/fonts/Type1
type1:pri=50 -> /usr/share/fonts/default/Type1
This will add /usr/share/X11/fonts/misc as the first FPE with the attribute
the attribute unscaled etc. This is functionally equivalent to setting
the following font path:
General information: X(7)
- Initial access control list for display number n
- Bitmap font directories
- Outline font directories
- Unix domain socket for display
- Error log file for display number n if run from
- Default error log file if the
server is run from xdm(1)
X Window System Protocol, The X Font Service Protocol, X Display Manager
, X Logical Font Description Conventions
Starting the server: startx(1)
Controlling the server once started: xset(1)
man pages: Xorg(1)
Server internal documentation: Definition of the Porting Layer
for the X v11 Sample Server
The sample server was originally written
by Susan Angebranndt, Raymond Drewry, Philip Karlton, and Todd Newman,
from Digital Equipment Corporation, with support from a large cast. It
has since been extensively rewritten by Keith Packard and Bob Scheifler,
from MIT. Dave Wiggins took over post-R5 and made substantial improvements.
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